The present invention relates to a semiconductor light-emitting device arranged on an insulating substrate, and particularly to a semiconductor light-emitting device consisting essentially of gallium nitride compound semiconductors formed on a sapphire substrate.
In recent years, attention has been paid to gallium nitride-based compound semiconductors, such as GaN, as materials of short-wavelength light emitting diodes (LED) or semiconductor laser devices (LD) for use in a range between blue light and ultraviolet. It is expected that a blue light semiconductor laser device using such a material will be applied to a light source for high-density information processing, because of its short oscillation wavelength.
Conventionally, gallium nitride-based compound semiconductor layers are grown and stacked on a sapphire substrate. Where an electrical contact is formed on a layer close to the substrate, among the stacked layers on the substrate, it is necessary to etch and remove part of the surface-side layers, since sapphire is insulating. In a device, such as a light-emitting diode, in which the whole light-emitting intensity is important, the above-described etching process should be considered, because it decreases the light-emitting area of the device, thereby directly lowering the light-emitting intensity.
As shown in Jpn. Pat. Appln. KOKAI Publication No. 6-338632, it has been proposed to arrange a pair of electrodes on diagonally opposite sides in order to increase the light-emitting area. However, this publication only shows a relationship between the position of the electrodes and effective flow of electric current, and does not refer to a method of increasing the light-emitting area or decreasing the electrode area. From the point of view of increasing the light-emitting area itself, it is preferable to lead an electrode out through a hole formed in a top surface, as shown in Jpn. Pat. Appln. KOKAI Publication No. 4-273175. In this proposal, however, since the light-emitting area is shielded by an expanded electrode when viewed from the top, the light-emitting area is substantially not increased.
As described above, a light-emitting device of compound semiconductors arranged on an insulating substrate needs to have a pair of electrodes arranged on its light-output face. Since the electrodes need to be connected to bonding wires, and thus should not be so small, the electrodes cause a decrease in the light-emitting area.